Efficiency

The SPEEDHUB’s mechanical efficiency matches that of a good derailleur system.

Drive	Efficiency
SPEEDHUB 500/14, gears 1–7	about 96%
SPEEDHUB 500/14, gears 8–14	about 98%
Derailleur, depending on teeth, chain angle and wear	95–98.5%
Conventional 7–8-speed hub gear	about 90% (1st gear) – 98% (direct gear)

A derailleur’s losses come from the bottom bracket, chain, sprockets and hub, and depend mainly on tooth counts, chain angle and wear. On a SPEEDHUB the chain runs straight from a single large chainring, and the loss depends on the gear selected. Both lie between 1.5% and 5%. Conventional hub gears drop off sharply in the low and high gears — the SPEEDHUB does not. That is down to large tooth counts, needle bearings in the planet gears, oil lubrication and very stiff parts.

Two kinds of loss

Load-independent is the friction of the seals: whether you push the bike, roll downhill or climb out of the saddle, it is the same. Depending on speed it is one to three watts — little, but enough to stop a wheel spun in a workstand after a few turns, or to turn the cranks when you push the bike. You see it straight away.

Load-dependent is the friction of gears and bearings under load: a percentage of the power transmitted. At 95% efficiency, 5 W of 100 W is lost, 15 W of 300 W, and 50 W of a 1,000 W sprint. You cannot see it in a workstand; only a test rig or measured rides show it — yet this is what really counts.

An example: you climb at 200 W. In the SPEEDHUB’s 4th gear — equivalent to 1st gear on a seven-speed hub — at 96% efficiency you lose 8 W; with the seven-speed hub, 20 W. Add 2 W for the seals and it is still 10 W against 20 W. Seal friction is like a lightly rubbing brake pad: it soon stops a freely spinning wheel, but you barely feel it when riding.

Pedalling backwards

When you pedal backwards, the sprocket turns backwards too and reverses how the planetary gear works: the sun gears, normally locked to the axle, now ratchet round, which means more friction. Freewheeling — the normal situation — the sun gears stand still. Unlike on a derailleur, then, backpedalling is not the same as a rolling wheel with the cranks still.

In practice

In marathon mountain-bike races, riders on SPEEDHUBs rode the same or better times than on derailleurs. The same times make sense, since the losses barely differ. The better times come from shifting faster and more often with a SPEEDHUB — so you are in the right gear more of the time.

That is the efficiency that matters most: yours. In the right gear, your muscles turn about 25% of your breakfast calories into forward motion. In the wrong gear you either push harder (heavy legs) or spin faster (racing pulse) — and your efficiency can drop below 10%. The SPEEDHUB is designed so you always shift to the right gear in time, in one movement.